Data from wrong IOL patient safety incidents (PSIs) submitted to the National Reporting and Learning System (2010–2014) were reviewed and scrutinised by thematic analysis and compared with the historical data collected for groups in 2003-2010, prior to the mandatory checklist use. One hundred and seventy-eight wrong IOL, PSIs were identified. The contributory factors included: transcription errors (n=26); wrong patient biometry (n=21); wrong IOL selection (n=16); changes in planned procedure (n=16); incorrect IOL brought into theatre (n=11); left / right eye selection errors (n=9); communication errors (n=9); and positive / negative IOL power errors (n=9). In 44 PSIs, no causal factor was reported, limiting the learning value of such reports. Compared with the data from 2003-2010 of 164 incidents, although biometry errors were much reduced, IOL transcription and documentation errors were greater, particularly if further checks did not refer to the original source documentation. The majority of errors were detected postoperatively as refractive surprises and reduced visual acuity. IOL exchange surgery was reported in 45 cases. Wrong IOL implantation is a serious patient safety incident and is defined by NHS England as an Adverse Event. These incidents, however, continue to occur despite surgical checklists and patient safety initiatives and may be under-reported. Human factors are heavily implicated and consistent checks, scenario based simulation training, detailed incident reporting and causal analysis is recommended to enhance patient safety.